1. Field of the Invention
The present invention relates to a webbing winding device that transmits urging force to a spool on which a webbing that is applied to an occupant of a vehicle is wound and unwound.
2. Related Art
In a webbing winding device recited in Japanese Patent Application Laid-Open (JP-A) No. 2001-233175, adapters (a first adapter and a second adapter) are provided between a spool and a spiral coil spring, and torsion coil springs (a first torsion coil spring and a second torsion coil spring) are provided at outer peripheries of the adapters.
When the first torsion coil spring is tightly wound on the outer peripheries of the first adapter and the second adapter, turning between the first torsion coil spring and the first adapter and second adapter is limited (regulated), and a rotational urging force is transmitted from the spiral coil spring to the spool.
Subsequently, when the second torsion coil spring is tightly wound on the outer periphery of the second adapter, turning between the second torsion coil spring and the second adapter is limited (regulated), and the rotational urging force that is transmitted from the spiral coil spring to the spool is reduced.
However, in this webbing winding device, a limiting torque between a torsion coil spring and an adapter when the torsion coil spring is not tightly wound on the adapter needs to be small, while a limiting torque between the torsion coil spring and the adapter when the torsion coil spring is tightly wound on the adapter needs to be large. For the difference between the two limiting torques to be large, a number of coils of the torsion coil spring needs to be large.
Now, if the number of coils of the torsion coil spring is increased, both the torsion coil spring and the adapter are longer, and a space for arrangement of the torsion coil spring and the adapter is larger.
Accordingly, it is desired that the difference between the two limiting torques may be increased without increasing the number of coils of the torsion coil spring.